Heterojunction material, preparation method thereof and application of heterojunction material in photocatalytic degradation of perfluorooctanoic acid

Abstract

The invention discloses a heterojunction material, a preparation method thereof and application of the heterojunction material in photocatalytic degradation of perfluorooctanoic acid. The preparation method of the heterojunction material comprises the following steps: dissolving a bismuth salt in a solvent, adding an iodized salt and a transition metal oxide MOx, mixing to obtain a mixed solution, and carrying out a constant-temperature hydrothermal reaction to obtain the heterojunction material. According to the invention, two inorganic semiconductors bismuth oxyiodate and transition metal oxide MOx are compounded to obtain the heterojunction material. In the material, bismuth oxyiodate and MOx form a heterojunction, carrier recombination is inhibited, the photocatalytic performance is improved, the material can be used as a photocatalyst, and the perfluorooctanoic acid is efficiently degraded through two different paths while the solar energy utilization rate is improved. The bottleneck problem that perfluoro caprylic acid residues cannot be thoroughly cleaned, degraded and degraded in the field is solved, perfluoro caprylic acid is converted into volatile perfluoroalkane, and wide application prospects are achieved.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic materials technology, and in particular to a heterojunction material, its preparation method, and its application in the photocatalytic degradation of perfluorooctanoic acid. Background Technology

[0002] Perfluorooctanoic acid (PFOA) is the most typical perfluorinated and polyfluoroalkyl substance and also the most abundant pollutant in the environment. Due to its widespread industrial applications, such as in textiles, cookware, and medical devices, PFOA levels in the environment have been increasing year by year. It has strong biotoxicity and is classified as a Group I pollutant, and its high carbon-fluorine bond energy (approximately 116 kcal / mol) further contributes to its high environmental toxicity. -1 Perfluorooctanoic acid (PFOA) is difficult to degrade effectively using conventional treatment methods and has strong environmental persistence, making it one of the most difficult-to-treat and highly toxic pollutants in the environment. Therefore, it is necessary to explore green and effective methods for removing PFOA.

[0003] Among various methods for removing perfluorooctanoic acid (PFOA), photocatalysis has become a promising technology for the degradation of perfluorocarboxylic acids due to its lack of the need for external reducing or oxidizing agents, absence of secondary pollution, and the fact that the reaction occurs under mild pH and temperature conditions. However, currently designed photocatalysts for PFOA degradation are mainly based on stepwise decarboxylation-hydroxylation-elimination-hydrolysis pathways and hydrogen / fluorine exchange mechanisms. A common drawback of these processes is that the carbon chains of pollutants gradually shorten as the reaction proceeds, significantly increasing the difficulty of the reaction. Except for using high-energy photons (below 254 nm) to directly break stubborn carbon-fluorine and carbon-carbon bonds, most solar-responsive photocatalysts cannot generate enough reduction electrons and oxidation holes to completely defluorinate and degrade these still highly toxic short-chain substances. Therefore, it is necessary to develop a photocatalyst capable of deep and efficient degradation of PFOA under sunlight. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a BiOIO3-MO with a long triplet lifetime. x Heterojunction photocatalysts, with their long-lived triplet states, mediate the oxidative addition, transition state, and reductive elimination processes in nucleophilic fluorination reactions centered on fluoride ions, thereby completely degrading perfluorooctanoic acid (PFOA).

[0005] The technical solution of the present invention is as follows: A method for preparing a heterojunction material, the method comprising: dissolving a bismuth salt in a solvent, adding an iodide salt and a transition metal oxide (MO) x The mixture is mixed to obtain a mixed solution, which is then subjected to a constant-temperature hydrothermal reaction to obtain the heterojunction material.

[0006] According to an embodiment of the present invention, the bismuth salt may be selected from at least one of bismuth nitrate pentahydrate, bismuth sulfate, and bismuth chloride, for example, bismuth nitrate pentahydrate.

[0007] According to an embodiment of the present invention, the iodine-containing oxide may be selected from at least one of potassium iodate, diiodine pentoxide, and potassium iodide, for example, diiodine pentoxide.

[0008] According to an embodiment of the present invention, the transition metal oxide MO x M is selected from at least one of Cu, Zn, Fe, Ti, Mn, V, Co, and Ni. Preferably, the valence state of the M metal ion is divalent or trivalent. Further, the MO x It can be obtained through methods known in the art, such as commercial purchase.

[0009] According to an embodiment of the present invention, the solvent may be selected from at least one of water, ethanol, and dilute nitric acid, for example, water.

[0010] According to an embodiment of the present invention, the concentration of bismuth salt in the mixed solution is 5-15 g / L, for example, 7.5 g / L.

[0011] According to an embodiment of the present invention, the concentration of iodized salt in the mixed solution is 1-10 g / L, for example, 5 g / L.

[0012] According to an embodiment of the present invention, MO in the mixed solution x The concentration is 10-30 g / L, for example, 20 g / L.

[0013] According to an embodiment of the present invention, the conditions for the isothermal hydrothermal reaction include: a reaction temperature of 120-220 °C, for example 180 °C; and a reaction time of 10-16 h, for example 12 h.

[0014] According to an embodiment of the present invention, after the heterojunction material is obtained by the isothermal hydrothermal reaction, the heterojunction material can be further subjected to centrifugal cleaning and / or vacuum drying. Preferably, the cleaning solvent used for centrifugal cleaning can be a solvent known in the art, such as water, methanol, or ethanol, and the cleaning is performed at least three times.

[0015] Preferably, centrifugation conditions known in the art can be used for centrifugation cleaning, such as a centrifugation speed of 5000-10000 r / min, for example 8000 r / min, and a centrifugation time of at least 5 min.

[0016] Preferably, the vacuum drying conditions include: a vacuum drying temperature of 60-100 ℃, for example, 60 ℃; and a drying time of at least 10 h, for example, 18 h.

[0017] A heterojunction material comprising bismuth iodate and metal oxide MO x Bismuth iodate and metal oxide MO x A heterojunction structure was formed between them.

[0018] According to an embodiment of the present invention, the mass content of bismuth oxyiodate in the heterojunction material is 15%-40%, 20%, 25%, 30%, 35%, or 40%.

[0019] According to an embodiment of the present invention, in the heterojunction material, the metal oxide MO x The mass content is 60%-85%, for example, 65%, 70%, 75%, 80%.

[0020] According to an embodiment of the present invention, the heterojunction material is obtained by the above preparation method.

[0021] The present invention also provides a photocatalyst, wherein the photocatalyst comprises the above-mentioned heterojunction material.

[0022] The present invention also provides the application of the above-mentioned heterojunction material and / or photocatalyst in photocatalysis, preferably for the degradation of perfluorooctanoic acid.

[0023] The present invention also provides a method for degrading perfluorooctanoic acid (PFOA), the method comprising the following steps: dispersing the above-mentioned photocatalyst in a solution containing PFOA, and carrying out a degradation reaction under light irradiation to obtain degradation products.

[0024] According to an embodiment of the present invention, the concentration of the photocatalyst in the reaction system is 0.1-1 g / L, for example, 0.5 g / L.

[0025] According to an embodiment of the present invention, the solution containing perfluorooctanoic acid is preferably an aqueous solution of perfluorooctanoic acid with a concentration of 0.01-4 g / L, for example, 2 g / L.

[0026] According to an embodiment of the present invention, the illumination can be sunlight, xenon lamp, mercury lamp, or preferably sunlight.

[0027] According to an embodiment of the present invention, the degradation reaction can be carried out in a photoreactor known in the art, such as a light-transmitting reactor.

[0028] According to an embodiment of the present invention, the illumination conditions include: a light intensity of 0.1-2 W / cm². 2 For example, 0.5 w / cm 2 The light exposure time should be at least 1 hour, for example, more than 3 hours.

[0029] According to an embodiment of the present invention, the degradation rate of perfluorooctanoic acid is greater than 99%, for example, 99.6%, through the above degradation reaction.

[0030] According to an embodiment of the present invention, the degradation products obtained after the above degradation reaction include perfluoroalkane, fluoride ions, and short-chain perfluorocarboxylic acids. Preferably, the perfluoroalkane has the molecular formula C8F. 18 C7F 16 C6F 14 C5F 12 C4F 10 With C3F8. Preferably, the molecular formula of the short-chain perfluorocarboxylic acid is C6F8. 13 COOH, C5F 11 COOH, C4F9COOH, C3F8COOH, C2F5COOH, CF3COOH.

[0031] According to an embodiment of the present invention, in the degradation products, perfluoroalkanes account for more than 20% of the total fluorine, for example, 23%; fluoride ions account for more than 65% of the total fluorine, for example, 71%; and short-chain perfluorocarboxylic acids account for less than 4% of the total fluorine, for example, 2%. In the present invention, total fluorine refers to the total molar amount of fluorine in the initial perfluorooctanoic acid, and the proportion of total fluorine refers to the molar proportion of fluorine content in the degradation products to the total fluorine content.

[0032] Beneficial effects 1) This invention combines two inorganic semiconductors, bismuth oxyiodate and transition metal oxide MO. x BiOIO3-MO obtained by recombination x Heterojunction materials, BiOIO3 and MO x The formation of a heterojunction suppresses carrier recombination and improves photocatalytic performance, allowing it to serve as a photocatalyst that efficiently degrades perfluorooctanoic acid (PFOA) via two different pathways while simultaneously increasing solar energy utilization. On one hand, it can degrade PFOA to produce short-chain perfluorocarboxylic acids via the normal chain shortening pathway; on the other hand, thanks to the long triplet lifetime of BiOIO3 material, it can degrade MO under sunlight. x The toxic short-chain perfluorocarboxylic acids produced by the degradation of perfluorooctanoic acid (PFOA) are converted into perfluoroalkanes and released into the water, where they are neutralized by ozone in the air, thus completely eliminating PFOA pollutants from the water. In other words, the heterojunction material of this invention can promote the conversion of PFOA and the resulting short-chain perfluorocarboxylic acids into perfluoroalkanes, thereby preventing the accumulation of toxic perfluorocarboxylic acids. This invention overcomes the bottleneck problem in the field of completely cleaning and degrading PFOA residues, converting PFOA into volatile perfluoroalkanes, and has broad application prospects.

[0033] 2) The heterojunction photocatalyst of the present invention exhibits excellent performance in the degradation of perfluorooctanoic acid (PFOA), and can degrade more than 99.9% of PFOA in solution. The main products are fluoride ions and perfluoroalkanes, which are very easy to recover or remove.

[0034] 3) The heterojunction photocatalyst of the present invention exhibits good stability in multiple cycles when degrading perfluorooctanoic acid.

[0035] 4) The heterojunction photocatalyst of the present invention can use solar energy as the driving force, which reduces the reaction cost, avoids secondary pollution and other problems, and solves the problem of difficult degradation of perfluorooctanoic acid.

[0036] 5) The photocatalyst preparation method of the present invention is simple and easy to operate. Attached Figure Description

[0037] Figure 1 The images shown are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the BiOIO3-TiO2 prepared in Example 1. Figure 2 The X-ray photoelectron spectrum of BiOIO3-TiO2 prepared in Example 1 is shown below. Figure 3 This is a chromatogram showing the product analysis of the photocatalytic degradation of perfluorooctanoic acid using the catalyst prepared in Example 1; Figure 4 The graphs show the performance test results of the photocatalytic degradation of perfluorooctanoic acid by the catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2. Figure 5 The figures show the cycle stability of the photocatalytic degradation of perfluorooctanoic acid (PFOA) by BiOIO3-TiO2 in Application Example 1, and the performance test figures of the photocatalysts for PFOA degradation in Application Examples 2-4. Detailed Implementation

[0038] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0039] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0040] Example 1 A heterojunction photocatalyst BiOIO3-MO x The preparation method is as follows: 375 mg of bismuth nitrate pentahydrate and 250 mg of iodine pentoxide were weighed and dispersed in 50 mL of water. The mixture was ultrasonically stirred for 30 min to ensure uniform dispersion. Then, 1 g of TiO2 was added, and the mixture was ultrasonically stirred for another 30 min. The resulting solution was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and heated at 180 °C for 12 h. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and washed three times with water. The washed solid was then vacuum-dried overnight at 60 °C to obtain the heterojunction photocatalyst BiOIO3-TiO2, in which the mass ratio of BiOIO3 to TiO2 was approximately 3:10.

[0041] according to Figure 1 and Figure 2 It can be seen that a heterojunction structure is formed between bismuth oxyiodate and the metal oxide TiO2 in the heterojunction photocatalyst BiOIO3-TiO2.

[0042] Example 2 The preparation method of the photocatalyst in this embodiment is basically the same as that in Example 1, except that: Replace the hydrothermal temperature of 180 °C in step (1) of Example 1 with 140 °C, while keeping other conditions unchanged, to obtain a heterojunction photocatalyst, denoted as 140-BiOIO3-TiO2.

[0043] Example 3 The preparation method of the photocatalyst in this embodiment is basically the same as that in Example 1, except that: Replace the hydrothermal temperature of 180 °C in step (1) of Example 1 with 160 °C, while keeping other conditions unchanged, to obtain a heterojunction photocatalyst, denoted as 160-BiOIO3-TiO2.

[0044] Example 4 The preparation method of the photocatalyst in this embodiment is basically the same as that in Example 1, except that: Replace the hydrothermal temperature of 180 °C in step (1) of Example 1 with 200 °C, while keeping other conditions unchanged, to obtain a heterojunction photocatalyst, denoted as 200-BiOIO3-TiO2.

[0045] Example 5 The preparation method of the photocatalyst in this embodiment is basically the same as that in Example 1, except that: Replace the hydrothermal temperature of 180 °C in step (1) of Example 1 with 220 °C, while keeping other conditions unchanged, to obtain a heterojunction photocatalyst, denoted as 220-BiOIO3-TiO2.

[0046] The mass ratio of BiOIO3 to TiO2 components in the catalysts prepared in Examples 2-5 is basically the same as that in Example 1.

[0047] Example 6 The preparation method of the photocatalyst in this embodiment is basically the same as that in Example 1, except that: The amount of TiO2 added in step (1) of Example 1 was replaced with 0.5 g, and other conditions remained unchanged, to obtain a heterojunction photocatalyst, denoted as BiOIO3-0.5-TiO2, in which the mass ratio of BiOIO3 to TiO2 components in the catalyst was approximately 3:5.

[0048] Example 7 The preparation method of the photocatalyst in this embodiment is basically the same as that in Example 1, except that: The amount of TiO2 added in step (1) of Example 1 was replaced with 0.75 g, and other conditions remained unchanged, to obtain a heterojunction photocatalyst, denoted as BiOIO3-0.75-TiO2, in which the mass ratio of BiOIO3 to TiO2 components in the catalyst was approximately 2:5.

[0049] Example 8 The preparation method of the photocatalyst in this embodiment is basically the same as that in Example 1, except that: The amount of TiO2 added in step (1) of Example 1 was replaced with 1.25 g, and other conditions remained unchanged, to obtain a heterojunction photocatalyst, denoted as BiOIO3-1.25-TiO2, in which the mass ratio of BiOIO3 to TiO2 components in the catalyst was approximately 6:25.

[0050] Example 9 The preparation method of the photocatalyst in this embodiment is basically the same as that in Example 1, except that: The amount of TiO2 added in step (1) of Example 1 was replaced with 1.5 g, and other conditions remained unchanged, to obtain a heterojunction photocatalyst, denoted as BiOIO3-1.5-TiO2, in which the mass ratio of BiOIO3 to TiO2 components in the catalyst was approximately 1:5.

[0051] Comparative Example 1 Preparation of catalyst BiOIO3: 375 mg of bismuth nitrate pentahydrate and 250 mg of iodine pentoxide were weighed and dispersed in 50 mL of water. The mixture was ultrasonically stirred for 30 min to ensure uniform dispersion. The resulting solution was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and heated at 180 °C for 12 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and washed three times with water. The washed solid was then vacuum-dried overnight at 60 °C to obtain the catalyst BiOIO3.

[0052] Comparative Example 2 The heterojunction photocatalyst BiOIO3-MO in this comparative example x The preparation method is basically the same as in Example 1, except that after obtaining the heterojunction photocatalyst BiOIO3-TiO2 through hydrothermal reaction, it is then calcined at 400℃ for 2 hours, denoted as 400-BiOIO3-TiO2. The mass ratio of BiOIO3 to TiO2 components in the catalyst prepared in Comparative Example 2 is basically the same as in Example 1.

[0053] Application Example 1 Photocatalytic perfluorooctanoic acid degradation performance test: 25 mg of the photocatalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2, and TiO2 were respectively added to 50 mL of a 100 mg / L perfluorooctanoic acid aqueous solution, and ultrasonically stirred for 10 min to ensure uniform dispersion. Then, at 0.5 w / cm 2 The catalytic reaction was carried out under simulated solar spectrum illumination with stirring, while the reaction temperature was maintained at 25 °C via a circulating water cooler. During the catalytic reaction, 1 mL of gas and solution were taken from the reactors of different reaction mixtures. The gas products were monitored using gas chromatography-mass spectrometry (GC-MS), and the liquid products were detected using liquid chromatography-mass spectrometry (LC-MS) and ion chromatography. Figure 3 As shown, the gaseous products include C8F. 18 C7F 16 C6F 14 C5F 12 C4F 10 Along with C3F8, the liquid products include C6F. 13 COOH (PFHpA), C5F 11 COOH (PFHxA), C4F9COOH (PFPeA), C3F8COOH (PFBA), C2F5COOH (PFPrA), CF3COOH (TFA), fluoride ions (F-) and formic acid (HCOOH), among which the multiplets of the gaseous products perfluoroalkanes are isomers of the corresponding products.

[0054] Figure 4 The figures show the performance test results of photocatalytic perfluorooctanoic acid (PFOA) degradation using different photocatalysts. Comparative Examples 1, 2, and TiO2 photocatalysts showed very low PFOA degradation and defluorination rates, with no perfluoroalkane formation. However, the heterojunction photocatalyst prepared in Example 1 exhibited excellent PFOA degradation and defluorination rates, producing perfluoroalkanes, with a degradation rate of up to 99.9%, a defluorination rate of up to 71%, and a perfluoroalkane yield of 23%.

[0055] Figure 5In Figure (a), the BiOIO3-TiO2 photocatalyst prepared in Example 1 is used for the photocatalytic degradation of perfluorooctanoic acid. After five cycles, the heterojunction photocatalyst still exhibits good photocatalytic activity and good stability.

[0056] Application Example 2 The photocatalytic degradation reaction of perfluorooctanoic acid in this application example is basically the same as in application example 1, except that the photocatalyst 140-BiOIO3-TiO2 from examples 2, 3, 4, and 5 is used respectively. 2x 160-BiOIO3-TiO2, 200-BiOIO3-TiO2, and 220-BiOIO3-TiO2 were used for photocatalytic degradation of perfluorooctanoic acid.

[0057] like Figure 5 As shown in (b), the product type did not change compared to Application Example 1, but the degradation rate, defluorination rate and perfluoroalkane yield of perfluorooctanoic acid changed, indicating that the hydrothermal temperature during the synthesis of heterojunction materials affects the catalytic performance of the photocatalyst.

[0058] Application Example 3 The photocatalytic degradation reaction of perfluorooctanoic acid in this application example is basically the same as in application example 1, except that the BiOIO3-0.25-TiO2, BiOIO3-0.75-TiO2, BiOIO3-1.25-TiO2, and BiOIO3-1.75-TiO2 photocatalysts of examples 6, 7, 8, and 9 are used respectively.

[0059] like Figure 5 As shown in (c), the product type remained unchanged compared to Application Example 1, but the degradation rate, defluorination rate, and perfluoroalkane yield of perfluorooctanoic acid changed, indicating that MO x The amount of [amount] will affect the catalytic performance of the photocatalyst.

[0060] Application Example 4 The photocatalytic degradation reaction of perfluorooctanoic acid in this application example is basically the same as in Application Example 1, except that 0.3, 0.4, 0.6, and 0.7 w / cm³ are used respectively. 2 The intensity of the light simulates sunlight.

[0061] like Figure 5 As shown in (d), the product type did not change compared to Application Example 1. The degradation rate, defluorination rate and perfluoroalkane yield of perfluorooctanoic acid did not change much, and it still showed good photocatalytic activity.

[0062] Comparative Application Example 1 The photocatalytic degradation reaction of perfluorooctanoic acid in this comparative application example is basically the same as in application example 1. The difference is that blank experiments were conducted under the conditions of no catalyst, no perfluorooctanoic acid solution but pure water instead, and no light exposure. In this case, there was no phenomenon of perfluorooctanoic acid degradation and / or the formation of fluoride ions and perfluoroalkanes.

[0063] The exemplary embodiments of the present invention have been described above. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a heterojunction material, characterized in that, The preparation method includes: dissolving bismuth salt in a solvent, adding iodide salt and transition metal oxide MO. x The mixture is mixed to obtain a mixed solution, which is then subjected to a constant-temperature hydrothermal reaction to obtain the heterojunction material.

2. The preparation method according to claim 1, characterized in that, The bismuth salt is selected from at least one of bismuth nitrate pentahydrate, bismuth sulfate, and bismuth chloride; The iodine-containing oxide is selected from at least one of potassium iodate, iodine pentoxide, and potassium iodide; The transition metal oxide MO x M is selected from at least one of Cu, Zn, Fe, Ti, Mn, V, Co, and Ni; the valence state of the M metal ion is divalent or trivalent; The solvent is selected from at least one of water, ethanol, and dilute nitric acid.

3. The preparation method according to claim 1 or 2, characterized in that, The concentration of bismuth salt in the mixed solution is 5-15 g / L; The concentration of iodized salt in the mixed solution is 1-10 g / L; MO in the mixed solution x The concentration is 10-30 g / L.

4. The preparation method according to any one of claims 1-3, characterized in that, The conditions for the isothermal hydrothermal reaction include: a reaction temperature of 120-220 ℃ and a reaction time of 10-16 h; After obtaining the heterojunction material through the isothermal hydrothermal reaction, the heterojunction material is further subjected to centrifugal cleaning and / or vacuum drying.

5. The preparation method according to any one of claims 1-4, characterized in that, During centrifugal cleaning, the centrifugation speed is 5000-10000 r / min; The conditions for vacuum drying include: a vacuum drying temperature of 60-100 ℃; and a drying time of at least 10 hours.

6. A heterojunction material, characterized in that, The heterojunction material includes bismuth oxyiodide and metal oxide MO. x Bismuth iodate and metal oxide MO x A heterojunction structure was formed between them; In the heterojunction material, the mass content of bismuth iodate is 15%-40%; the metal oxide MO x The mass content is 60%-85%; The heterojunction material is obtained by the preparation method according to any one of claims 1-5.

7. A photocatalyst comprising the heterojunction material of claim 6.

8. The application of the heterojunction material of claim 6 and / or the photocatalyst of claim 7 in photocatalysis.

9. A method for degrading perfluorooctanoic acid, characterized in that, The method includes the following steps: dispersing the photocatalyst of claim 7 in a solution containing perfluorooctanoic acid, and carrying out a degradation reaction under light irradiation to obtain degradation products.

10. The method according to claim 9, characterized in that, The concentration of the photocatalyst in the reaction system is 0.1-1 g / L; The solution containing perfluorooctanoic acid is an aqueous solution of perfluorooctanoic acid with a concentration of 0.01-4 g / L; The lighting options include sunlight, xenon lamps, and mercury lamps. The lighting conditions include: light intensity of 0.1-2 W / cm². 2 The light exposure time should be at least 1 hour. Through the above degradation reaction, the degradation rate of perfluorooctanoic acid is greater than 99%.

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